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# 2.4 Mechanical Energy by ajizai

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```									EK = ½ m v 2                                                                                 Em = EK + E P

Science 10 – Mechanical Energy                                     Name_____________________

Total _________/13

1. A kicker on a football team kicks a football that travels on a
trajectory, as shown on the diagram. (7 marks):
a. What types of energy does the ball have, at the moment
that is leaves the kicker’s foot?

b. What types of energy does the ball have, at a point halfway from the ground to its highest
point?

c. What types of energy does the ball have, at the highest point of its path?

d. At what part of its motion are the kinetic and the potential energy equal to each other?

e. At what part of its motion is the kinetic energy the least?

f.   At what part of its motion is the gravitational potential energy the least?

g. Where is the total mechanical energy the greatest? Explain

2. An average force of 40.0 N is needed to compress a spring by 0.100 m. A 10.0 g ball is placed on the
spring. (7 marks)
a. How much work was done to compress the spring?

b. Once the spring is compressed, what has happened to the work that was done? (What form is
the energy in now?)

c. If the spring is released, what happens to the energy of the ball?

d. How much energy will the ball have at the instant that the ball leaves the spring?
EK = ½ m v 2                                                                                        Em = EK + E P

e. What will be the speed of the ball as it leaves the spring?

f.   If the ball is fired straight up into the air, how much gravitational potential energy will it have at
its highest point?

g. How high will it get before it starts to fall again?

3. A 60.0 kg athlete jumps vertically upward from the ground, to a height of 0.910 m above the ground.
What was his initial vertical speed? (5 marks)

4. A 0.300 kg billiard ball is propelled from a table at a horizontal speed of 1.50 m/s. If the table is
1.30m above the floor, what is the mechanical energy of the ball at the instant that it leaves the
table? (4 marks)
EK = ½ m v 2                                                                                 Em = EK + E P

5. A 2.00 kg ball is suspended from a ceiling by a rope 1.50 m long. The ball is pulled sideways and up
until the rope is horizontal.
a. How much gravitational potential energy will the ball gain? (2 marks)

b. If the ball is released, what is the maximum speed of its swing? (2 marks)

c. Assume that the ball keeps swinging. Mark on the diagram the places where it will have
i. maximum gravitational potential energy
ii. maximum kinetic energy
iii. maximum mechanical energy (3 marks)

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